Projection-type video display devices using liquid crystal panels, with increasing opportunities to utilizing the devices in, for example, presentation halls and the like, are required to be simplified and reduced in price and, furthermore, to get high performance and high function.
Patent Literature 1 discloses a technique of compensating for defocus caused by a change in temperature with a simple mechanism.
Patent Literature 2 discloses a technique to use a planar mirror as a projection mirror.